Quick advice

[Rich_new]

Hi

Not sure where this should go so Mods can move if in wrong place...sorry

I'm patching a hole in the bottom of a car so it's about fist size and obviously i have a small patch of steel sheet to go over it to weld. I'm just wondering where i put the earth clamp??? it's not going to touch the chassis AND the plate at the same time as it's a crocodile clip....can it just clamp to the floorpan somewhere close?

Thanks

 

[gordon stephenson]

Weld a tab of clean metal to the patch and clamp your earth onto it, Strike on the edge of the new plate then move across to weld patch and floorpan together, when you have finished grind off the tab,

 

[FranV8]

Yes, just make sure it's a clean, bare piece of metal you attach to. Once you make your initial tack (which is best started on the bodywork side then onto the new plate) - the repair plate will also have a good earth connection and you can start your weld where you like.

I've also heard that it's good to disconnect teh alternator whilst welding, there used to be rumours that you could wreck the diode pack in them. Don't know how necessary that is these days, but better safe than sorry.

 

[Engineer]

Older cars can be earthed through the door striker plates, alternatively the bonnet closing catch very often also provides a good earth point.

Voltage spikes from welding can damage alternators, but far more serious is damage caused to ECU's, which can cost an awful lot of money to replace.

For anyone doing regular car welding its a very good idea to either make or buy a surge protector which connects over the battery terminals, which will prevent any electrical parts getting damaged.

 

[Rich_new]

well it's an old car so yeah i had better do that

So being as the chassis is already earthed i only need to earth the patch plate and that is what the Tab is for?...just to be clear in my own mind

 

[Engineer]

Put the earth clamp onto door striker plate, clean the area around where you need to do the repair with knotted wire brush on an angle grinder, cut some new 1.5mm plate so it overlaps the hole by about 20mm all round, hold the repair patch in place with a hammer handle, get a few good tack on it, and then weld round continuously.

There is no need whatsoever for welding tabs onto the repair patch, as this will be earthed directly to the floor pan, as long as you have done the preparation work properly.

 

[madkayaker]

get the earth as close as you can. don't forget to disconect the battary

 

[Rich_new]

Thanks for the replies, will have a bit of a practice and get it sorted